import java.util.Scanner;
public class circle{
    public static void main(String[] args){
        try(Scanner sc = new Scanner(System.in)){
            System.out.println("请输入圆的半径");
            double num = sc.nextDouble();
           
            System.out.print("半径为" + num + "的圆面积为");
            ab(num);
        }
    }
    public static void ab(double num){
        double result = num * num * 3.14;
        System.out.println(result);
    }
}